GaAs epilayers were grown on Ge by metal-organic chemical vapor deposition (MOCVD) with As or Ga prelayers. The grown epilayers were examined for surface morphology, antiphase domain (APD) presence, and optical quality using optical interference contrast microscopy, molten potassium hydroxide (KOH) etching, and photoluminescence (PL) spectroscopy. The As prelayer results in smooth, shiny, and APD-free epilayers with good optical quality. In contrast, the Ga prelayer results in a rough surface with APDs and higher carbon incorporation.

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Thermodynamic and nucleation behaviour of the Y2O3-Al2O3-Y3Al5O12 system has been studied. The change in free energy on the formation of a single YAG molecule from a stoichiometric melt of the Y2O3-Al2O3 system at equilibrium is evaluated numerically as a function of temperature. The chemical potentials of the species in the system are evaluated using the regular solution model. The interfacial tension between YAG(S) and Y2O3-Al2O3(L) is determined by calculating the excess energy associated with the interface. The thermodynamic data investigated are used to determine the nucleation parameters such as size, the free energy of formation of a critical nucleus for various possible shapes of clusters as a function of supercooling for different values of interfacial tension, and the shape factors which lead to the understanding of the nucleation phenomena of YAG.

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